Difference between revisions of "Opcode"

An opcode is a number representing an instruction for the F8 processor system to follow for example \$2B means No Operation (NOP). Programs are made up of opcodes, which instruct the F8 System to do something, such as load a register with a value, perform arithmetic on a register, change the program counter (jump), or input or output data through the ports. Opcodes in the F8 System are each one byte wide, though some may be followed by an address (two bytes) or a value for the opcode to use. Often people refer to the mnemonics as opcodes but these are just constructed so we people can understand it easier than just looking at rows of numbers. NOP is such a mnemonic and can be used in an assembly program listing.

The Instruction Set

In the information for each opcode, the following notations are used:

Opcode Notations
A Accumulator
P0 Program counter
P Program counter Stack
DC0 Data counter
DC1 Alternate data counter
W Status register
 0 to 11 Select registers r0-r11 I Select ISAR, then ISAR = ISAR + 1 S Select ISAR D Select ISAR, then ISAR = ISAR - 1
t 3-bit constant
i 4-bit constant
n 8-bit constant
nn 16-bit constant
( ) Contents of memory (e.g., (DC))
x Binary value placeholder
Status Flag Notations
O Overflow Flag
Z Zero Flag
C Carry Flag
S Sign Flag
0 Resets status flag
1 Sets status flag
X Modifies status flag
Table copied from F8_info
Extra data added from L. Turner F8 ins
Mnemonic Length Cycles Description Opcode Status Flags
Binary Hex O Z C S

8-bit Transfers

LR A, r 1 1 A = r  %0100xxxx \$4x - - - -
LR A, Ku 1 1 A = R12  %00000000 \$00 - - - -
LR A, Kl 1 1 A = R13  %00000001 \$01 - - - -
LR A, Qu 1 1 A = R14  %00000010 \$02 - - - -
LR A, Ql 1 1 A = R15  %00000011 \$03 - - - -
LR r, A 1 1 r = A  %0101xxxx \$5x - - - -
LR Ku, A 1 1 R12 = A  %00000100 \$04 - - - -
LR Kl, A 1 1 R13 = A  %00000101 \$05 - - - -
LR Qu, A 1 1 R14 = A  %00000110 \$06 - - - -
LR Ql, A 1 1 R15 = A  %00000111 \$07 - - - -
LM 1 2.5 A = (DC0), DC0 = DC0 + 1  %00010110 \$16 - - - -
ST 1 2.5 (DC0) = A, DC0 = DC0 + 1  %00010111 \$17 - - - -
LR A, IS 1 1 A = ISAR  %00001010 \$0A - - - -
LR IS, A 1 1 ISAR = A  %00001011 \$0B - - - -
LR J, W 1 1 R9 = W  %00011101 \$1D - - - -
LR W, J 1 2 W = R9  %00011110 \$1E - - - -
LISU i 1 1 ISAR(upper) = i  %01100xxx \$6x - - - -
LISL i 1 1 ISAR(lower) = i  %01101xxx \$6x - - - -
LI n 2 2.5 A = n  %00100000 %xxxxxxxx \$20 \$xx - - - -
LIS i 1 1 A = i  %0111xxxx \$7x - - - -
CLR 1 1 A = 0  %01110000 \$70 - - - -
Mnemonic Length Cycles Description Opcode Status Flags
Binary Hex O Z C S

16-bit Transfers

LR K, P 1 4 R12=P(upper), R13=P(lower)  %00001000 \$08 - - - -
LR H, DC 1 4 R10=DC0(upper), R11=DC0(lower)  %00010001 \$11 - - - -
LR Q, DC 1 4 R14=DC0(upper), R15=DC0(lower)  %00001110 \$0E - - - -
LR P, K 1 4 P(upper)=R12, P(lower)=R13  %00001001 \$09 - - - -
LR DC, H 1 4 DC0(upper)=R10, DC0(lower)=R11  %00010000 \$10 - - - -
LR DC, Q 1 4 DC0(upper)=R14, DC0(lower)=R15  %00001111 \$0F - - - -
DCI nn 3 6 DC0=nn  %00101010 %xxxxxxxx %xxxxxxxx \$2A \$xx \$xx - - - -
XDC 1 2 DC0=DC1, DC1=DC0  %00101100 \$2C - - - -
ADC 1 2.5 DC0=DC0+A  %10001110 \$8E - - - -

8-bit Arithmetic

AS r 1 1 A = A + r  %1100xxxx \$Cx X X X X
AI n 2 2.5 A = A + n  %00100100 %xxxxxxxx \$24 \$xx X X X X

Jumps

BR n 2 3.5 P0 = P0 + 1 + n  %10010000 %xxxxxxxx \$90 \$xx - - - -
BC n 2 3 (no branch)
3.5 (branch)
if CARRY: P0 = P0 + 1 + n  %10000010 %xxxxxxxx \$82 \$xx - - - -
BNC n 2 3 (no branch)
3.5 (branch)
if NO CARRY: P0 = P0 + 1 + n  %10010010 %xxxxxxxx \$92 \$xx - - - -
BP n 2 3 (no branch)
3.5 (branch)
if POSITIVE: P0 = P0 + 1 + n  %10000001 %xxxxxxxx \$81 \$xx - - - -
BM n 2 3 (no branch)
3.5 (branch)
if NEGATIVE: P0 = P0 + 1 + n  %10010001 %xxxxxxxx \$91 \$xx - - - -
BZ n 2 3 (no branch)
3.5 (branch)
if ZERO: P0 = P0 + 1 + n  %10000100 %xxxxxxxx \$84 \$xx - - - -
BNZ n 2 3 (no branch)
3.5 (branch)
if NOT ZERO: P0 = P0 + 1 + n  %10010100 %xxxxxxxx \$94 \$xx - - - -
BNO n 2 3 (no branch)
3.5 (branch)
if NO OVERFLOW: P0 = P0 + 1 + n  %10011000 %xxxxxxxx \$98 \$xx - - - -
BT t, n 2 3 (no branch)
3.5 (branch)
AND bitmask t with W, if result = TRUE: P0 = P0 + 1 + n  %10000xxx %xxxxxxxx \$8x - - - -
BF i, n 2 3 (no branch)
3.5 (branch)
AND bitmask i with W, if result = FALSE: P0 = P0 + 1 + n  %1001xxxx %xxxxxxxx \$9x - - - -
BR7 n 2 2 (no branch)
2.5 (branch)
if ISAR(lower) != 7: P0 = P0 + 1 + n  %10001111 %xxxxxxxx \$8F \$xx - - - -
JMP nn 3 5.5 P0 = nn, A is destroyed  %00101001 %xxxxxxxx %xxxxxxxx \$29 \$xx \$xx - - - -
LR P0, Q 1 4 P0(upper) = R14, P0(lower) = R15  %00001101 \$0D - - - -
Mnemonic Length Cycles Description Opcode Status Flags
Binary Hex O Z C S

Shifts

SL 1 1 1 Shift A left one bit, fill with %0  %00010011 \$13 0 X 0 X
SL 4 1 1 Shift A left four bits, fill with %0000  %00010101 \$15 0 X 0 X
SR 1 1 1 Shift A right one bit, fill with %0  %00010010 \$12 0 X 0 1
SR 4 1 1 Shift A right four bits, fill with %0000  %00010100 \$14 0 X 0 1

Misc.

COM 1 1 A = [[complement] of A (inverse)  %00011000 \$18 0 X 0 X
NOP 1 1 No operation (cycle waster)  %00101011 \$2B
EI 1 1 Enable interrupts in status register bit 4  %00011011 \$1B
DI 1 1 Disable interrupts in status register bit 4  %00011010 \$1A

Input/Output

IN n 2 4 Input port n to A  %00100110 %xxxxxxxx \$26 \$xx 0 X 0 X
INS i 1 2 (i=0-1)
4 (i=4-7)
Input port i to A  %1010xxxx \$Ax 0 X 0 X
OUT n 2 4 Output A to port n  %00100111 %xxxxxxxx \$27 \$xx - - - -
OUTS i 1 2 (i=0-1)
4 (i=4-7)
Output A to port i  %1011xxxx \$Bx - - - -

(rest of table to follow)